This invention pertains to synergistic herbicidal combinations, particularly such combinations for use in controlling weeds in a rice crop.
Molinate (S-ethyl hexahydro-1 H-azepine-1 -carbothioate) is a thiocarbamate herbicide which has been used to control weeds in rice crops for a number of years, and is generally sold under products bearing the trademark ORDRAM.RTM.. In different formulations and strengths, molinate is applied pre-plant, pre-flood or post-flood to control a wide range of weeds in rice crops, and is generally applied at rates ranging from about 500 to about 11,000 g/ha. However, as with many pesticides, it would be desirable to be able to achieve weed control while using a lower application rate of molinate. This could also result in less impact upon the environment and/or upon workers handling the product.
It has now been found that, surprisingly, combining of a lesser amount of the herbicide acetochlor with molinate can produce a synergistic effect such that equivalent weed control can be obtained with a lesser amount and/or application rate of molinate.
Acetochlor, or 2-chloro-2'-methyl-6'-ethyl-N(ethoxymethyl)acetanilide is an acetamide or haloacetanilide herbicide which is sold under several trademarks, notably SURPASS.RTM. and HARNESS.RTM., and in microencapsulated formulations under trademarks such as TOPNOTCH.TM. AND FULTIME.TM.. This herbicide is sold primarily for use in corn crops, and also is known to be useful for certain other crops such as soybeans. However, acetochlor is generally considered to be too injurious to rice to be used as the primary herbicide for controlling weeds in rice crops. In accordance with the present invention, however, the use of acetochlor in an amount which produces substantially no phytotoxicity to a rice crop, in combination with molinate, particularly a lesser amount or lower application rate than is normally used, produces a synergistic effect, resulting in good control of weeds in rice crops in either pre-flood or post-flood applications.